Temperature-Dependent Structure of A High-k (Ba,La)(Ti,Ce)O3 Ceramic

The lattice structure of a high-k BL3TC5 [(Ba1-xLax)(Ti1-x/4-yCey)O-3 (x = 0.03, y = 0.05)] ceramic with cubic structure at room temperature was investigated using temperature-dependent X-ray diffraction (XRD) and Raman spectroscopy. The XRD results indicated that with increasing temperature, the cubic lattice of BL3TC5 showed a lower coefficient of linear expansion (alpha = 7.7 x 10(-6)/degrees C) relative to the cubic BaTiO3 (9.3 x 10(-6)/degrees C), but no abnormal change in cell volume occurred around the dielectric peak temperature T-m (= 38 degrees C). The peak position of the similar to 835 cm(-1) Raman band induced by the substitution of La3+ ions for Ba sites in BL3TC5 was nearly independent of temperature on each side of T-m, whereas a slight fall (3 cm(-1)) in the peak position around T-m was detectable. The link between the dielectric peak with DPT and the lattice change was discussed.